This invention relates to a pattern selecting device for selecting few favorable candidate patterns from a plurality of candidate patterns. Such a pattern selecting device is particularly useful in a fingerprint search system for a criminal investigation.
A fingerprint search system uses a fingerprint collating device in collating an input fingerprint pattern with a plurality of registered fingerprint patterns. The fingerprint collating device successively produces first through N-th candidate pattern signals indicative of first through N-th candidate patterns where N represents an integer which is not less than two and is not greater than the number of the registered fingerprint patterns. In a descending order, the first through the N-th candidate pattern signals represent candidate degrees of similarity relative to the input fingerprint pattern. The number N is determined according to the type of the fingerprint collating device in the manner which will be described below.
A first type of the fingerprint collating device always produces the candidate pattern signals with a constant number used as the integer N. The integer N is, for example, equal to ten. Such a fingerprint collating device is called a fixed-number type.
In a second type of the fingerprint collating device, the number N is determined in accordance with the degree of similarity. Namely, the fingerprint collating device produces the candidate pattern signals having the candidate degrees which are not smaller than a predetermined value. Such a fingerprint collating device is called a fixed-similarity type.
After the first through the N-th candidate pattern signals are decided by the fingerprint collating device, an operator uses the fingerprint search system in visually comparing the input fingerprint pattern with the first through the N-th candidate patterns to detect an objective pattern which coincides with the input fingerprint pattern.
In the fixed-number type described above, a heavy work load is required on comparing the input fingerprint pattern with the first through the N-th candidate patterns no matter whether or not the objective pattern is included in the registered fingerprint patterns. This means that the operator must repeat invalid comparing operation if the objective pattern does not exist in the registered fingerprint patterns.
In the fixed-similarity type, the fingerprint collating device produces a reduced number of candidate pattern signals if the predetermined value is set at a large value. In this event, the work load of the operator is reduced. However, the objective pattern may be excluded from the candidate patterns because the input fingerprint pattern may comprise an obscure part so that none of the candidate patterns cannot get higher degree of similarity than the predetermined value.